Cache object numbers in CPDF_Parser::ParseIndirectObject().

R=jun_fang@foxitsoftware.com, tsepez@chromium.org

Review URL: https://codereview.chromium.org/1458633004 .

2 files changed, 34 insertions, 10 deletions

diff --git a/core/include/fpdfapi/fpdf_parser.h b/core/include/fpdfapi/fpdf_parser.h
index 174430e440..efb955be21 100644
--- a/core/include/fpdfapi/fpdf_parser.h
+++ b/core/include/fpdfapi/fpdf_parser.h
@@ -7,6 +7,8 @@
 #ifndef CORE_INCLUDE_FPDFAPI_FPDF_PARSER_H_
 #define CORE_INCLUDE_FPDFAPI_FPDF_PARSER_H_
 
+#include <map>
+
 #include "core/include/fxcrt/fx_system.h"
 #include "fpdf_objects.h"
 #include "third_party/base/nonstd_unique_ptr.h"
@@ -498,8 +500,6 @@ class CPDF_Parser {
 
   FX_DWORD LoadLinearizedMainXRefTable();
 
-  CFX_MapPtrToPtr m_ObjectStreamMap;
-
   CPDF_StreamAcc* GetObjectStream(FX_DWORD number);
 
   FX_BOOL IsLinearizedFile(IFX_FileRead* pFileAccess, FX_DWORD offset);
@@ -543,9 +543,22 @@ class CPDF_Parser {
   FX_DWORD m_dwFirstPageNo;
 
   FX_DWORD m_dwXrefStartObjNum;
+
+  // A map of object numbers to indirect streams. Map owns the streams.
+  CFX_MapPtrToPtr m_ObjectStreamMap;
+
+  // Mapping of object numbers to offsets. The offsets are relative to the first
+  // object in the stream.
+  using StreamObjectCache = std::map<FX_DWORD, FX_DWORD>;
+
+  // Mapping of streams to their object caches. This is valid as long as the
+  // streams in |m_ObjectStreamMap| are valid.
+  std::map<CPDF_StreamAcc*, StreamObjectCache> m_ObjCache;
+
   friend class CPDF_Creator;
   friend class CPDF_DataAvail;
 };
+
 #define FXCIPHER_NONE 0
 #define FXCIPHER_RC4 1
 #define FXCIPHER_AES 2
diff --git a/core/src/fpdfapi/fpdf_parser/fpdf_parser_parser.cpp b/core/src/fpdfapi/fpdf_parser/fpdf_parser_parser.cpp
index 6251748d3e..2105635687 100644
--- a/core/src/fpdfapi/fpdf_parser/fpdf_parser_parser.cpp
+++ b/core/src/fpdfapi/fpdf_parser/fpdf_parser_parser.cpp
@@ -141,6 +141,8 @@ void CPDF_Parser::CloseParser(FX_BOOL bReParse) {
     delete pStream;
   }
   m_ObjectStreamMap.RemoveAll();
+  m_ObjCache.clear();
+
   m_SortedOffset.RemoveAll();
   m_CrossRef.RemoveAll();
   m_V5Type.RemoveAll();
@@ -1200,16 +1202,23 @@ CPDF_Object* CPDF_Parser::ParseIndirectObject(CPDF_IndirectObjects* pObjList,
       (uint8_t*)pObjStream->GetData(), (size_t)pObjStream->GetSize(), FALSE));
   CPDF_SyntaxParser syntax;
   syntax.InitParser(file.get(), 0);
-  int32_t offset = GetStreamFirst(pObjStream);
-  for (int32_t i = GetStreamNCount(pObjStream); i > 0; --i) {
-    FX_DWORD thisnum = syntax.GetDirectNum();
-    FX_DWORD thisoff = syntax.GetDirectNum();
-    if (thisnum == objnum) {
-      syntax.RestorePos(offset + thisoff);
-      return syntax.GetObject(pObjList, 0, 0, pContext);
+  const int32_t offset = GetStreamFirst(pObjStream);
+
+  // Read object numbers from |pObjStream| into a cache.
+  if (m_ObjCache.find(pObjStream) == m_ObjCache.end()) {
+    for (int32_t i = GetStreamNCount(pObjStream); i > 0; --i) {
+      FX_DWORD thisnum = syntax.GetDirectNum();
+      FX_DWORD thisoff = syntax.GetDirectNum();
+      m_ObjCache[pObjStream][thisnum] = thisoff;
     }
   }
-  return nullptr;
+
+  const auto it = m_ObjCache[pObjStream].find(objnum);
+  if (it == m_ObjCache[pObjStream].end())
+    return nullptr;
+
+  syntax.RestorePos(offset + it->second);
+  return syntax.GetObject(pObjList, 0, 0, pContext);
 }
 
 CPDF_StreamAcc* CPDF_Parser::GetObjectStream(FX_DWORD objnum) {
@@ -1659,6 +1668,8 @@ FX_DWORD CPDF_Parser::LoadLinearizedMainXRefTable() {
     delete pStream;
   }
   m_ObjectStreamMap.RemoveAll();
+  m_ObjCache.clear();
+
   if (!LoadLinearizedAllCrossRefV4(m_LastXRefOffset, m_dwXrefStartObjNum) &&
       !LoadLinearizedAllCrossRefV5(m_LastXRefOffset)) {
     m_LastXRefOffset = 0;